Mechanical relay apparatus



March 30, 1937. .J. .F. SCHOCK MECHANICAL RELAY APPARATUS Filed Jan. 51,

INVENTOR. lAfizfM MafEfi-J 1 ATTORNEY.

Patented Mar. 30, 1937 UNITED STATES PATENT OFFICE 2,075,232 MECHANICALRELAY APPARATUS John F. Schock, Philadelphia, Pa., assignor to Leeds andNorthrup Company, Philadelphia, Pa., a corporation of PennsylvaniaApplication January 31, 1935, Serial No. 4,214

18 Claims.

- L. Y. Squibb, upon which the present applicaof movement, and asecondary member that is movable by or in accordance with the movementof the feelers into engagement with the primary movable member. Suchapparatus generally includes also a movable member effective tointegrate movements of the secondary movable member and operable therebythrough periodically engageable clutch mechanism and a suitable sourceof power.

In accordance with my invention, the response and accuracy of relayapparatus of the type just described, is for small deflections of theprimary movable member, controlled by provision for adjusting theclearance between the feelers and the primary movable member when inengaging relationship. Such an adjustment imparts to the apparatus thehighest degree of response and accuracy in cases where this is desired,while, on the other hand, permits a lower sensitivity to be obtainedwhen the apparatus is utilized in the measurement of a rapidly varyingquantity and it is desired to eliminate such rapid variations of lowamplitude, or in control systems in which too high a sensitivity maytend toward oscillation of the system.

On the other hand, the introduction of an appreciable clearance betweenthe feelers and the primary movable member may give rise to creeping,that is, cumulative errors imparted to the integrating mechanism, incase the timing of the feelers is not accurately adjusted. Therefore,further in accordance with my invention, I provide means forindependently adjusting the timing of the release of the feelers by themeans which operates to separate them intermittently.

For-a better understanding of my invention, together with other andfurther features thereof, reference is had to the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims. I

In the drawing, Fig. 1, is a view, in front elevation, of my improvedmechanical relay apparatus,,per se;

Fig. 2 is a cross-sectional view of the relay apparatus along the lines2-2 of Fig. 1 and including, also, a portion of an associated measuringinstrument of the type described in the above-mentioned Squibb patent.

Fig. 2a. is a detail of a bearing stud of Fig. 2;

Fig. 3 is a detail 'of the mechanism for adjusting the clearance betweenthe feelers and the primary movable element;

Fig. 4 is a detail view of the cam structure of Figs. 1 and 2 effectiveintermittently to separate the feelers; while Figs. 5 and 6 arecross-sectional views of the cam along the lines 55 and 6-6,respectively, of Fig. 4.

Referring now more particularly to Figs. 1 and 2 of the drawing, thereis shown a mechanical relay apparatus comprising a supporting base orplate Ill upon which are pivotally mounted a pair of feelers orscissors-like arms II and Ila having extending arms or brackets I2, I lasecured to pivot pins I3, I3a (only the bracket I2 and associated pivotI3 being shown in the drawing), which are supported between a bracket I4secured to the plate Ill and adjustable studs I5 and I5a. The studs I5,I5a are provided with cylindrical recesses IS?) in which are disposedhardened steel balls I5c forming bearings for the pivot pins I3, I3a.(Fig. 2a). The plate I0, omitted in Fig. 1 for the sake of clarity, isprovided with a projection Illa folded back substantially parallel tothe plate through which projects a screw I6 threaded into the plate I0and serving as a locking device for the studs I5, I51: which arethreaded through the plate l0 and projection Illa. A spring plate I! issecured to the depending arm of the bracket I4 to retain the pivot pinsI3, I31: in position and to provide a thrust for seating them accuratelyin the bearing recesses'of the studs I5, I512. The feelers II, IIa areprovided with extending arms l8, Illa, respectively, interconnected by abiasing spring I9, effective to urge the feelers II, Ila. intoengagement, thatis, to close the grips of the scissors. Attached to theextending brackets I2, I21:

with an upstanding arm or bracket; 33a thereof,

of the feelers II, He are cam followers 23, 23a,

respectively. r

The plate l3, upon which is secured the abovedescribed feelers, ismounted adjacent a continuously rotating shaft 2| upon which is secureda cam structure 22 (Figs. 4, 5 and 6) having cam elements 23 and 23acooperating with the cam followers 23, 23a intermittently to separatethe feelers lie for a predetermined portion of each revolution of theshaft 2|. The feelers Ila. are disposed to engage opposite sides of aprimary movable member, such as a deflecting pointer 24 secured to themovable coil 23 of a galvanometer assembly 23, only a fragmentaryportion of which is shown for the sake of clarity, since thegalvanometer may be of any of the several types well-known in the artand, pe se, constitutes no part of my present invention.

The feelers II, I la also engage opposite sides of a pin assembly 21interposed between the lower arms thereof and secured in a slot 23 of anupstanding bracket 29 of a secondary movable member or clutch member 33which, together is secured to a pivot pin 3| supported in a bearing inthe plate l3 and a second bearing in a bracket 32, a spring plate 32asecured to the bracket 32 being effective to retain the pivot pin 3|properly positioned within its bearings. A face plate 33, secured to thefront of the base |3 as by screws 33a, forms a bearing for the pivot pin3| to take the thrust of the spring plate 32a. The base plate l3 has apair of extending arms |3b pivoted at We in a supporting frame 34 of theapparatus, on which is mounted also the galvanometer assembly 23. Thebase plate l3 and the abovedescribed apparatus supported therefrom isbiased into engagement with the frame 34 as by a spring 35interconnecting the frame and the lower tip of the plate I3. Secured tothe base plate I3 are a pair of studs 33 provided with cam sur- ,faces33a. and secured in position by lock nuts 33b.

The cam surfaces 36a respectively cooperate with a pair of cam elements31, comprising an integral part of the cam structure 22, which areeffective intermittently to move the base plate i3 and its associatedapparatus about its pivot |3c through a small angle against the bias ofthe spring 35.

A detail of the structure of the pin assembly 21 is shown in Fig. 3.This assembly comprises a threaded stud 33 and a cooperating nut 39having guideways 39a which engage the edges of the slot 23 in which thepin assembly is supported to prevent rotation of right hand conicalmember 43. Loosely mounted on the stud 33 are a pair of frusto-conicalmembers 43 between which is supported an expansible split sleeve orcollar 4|. A locking key 42 is supported on the stud 33 and engages aflat 39b of the nut 33 and extends into the slit in the collar 4 I Theconical members 43 are urged into engagement by means of a nut 43 and alock nut 45 for maintaining the desired ,pin adjustment.

. disk 41 is actuated by the clutch member 33 disk 41 is mounted, may belocated a. mitable pulley or shaft 43 and slidewire or control disk 33.in case the apparatus is to be utilized in a re-' corder of the typedisclosed in the Squibb pat ent, the pulley 43 controlling the recordingpen and the disk 33, the measuringcircuit of the galvanometer, and/orany controlled circuit.

Referring to Fig. 2, there is also pivotallysupported at |3c a U-shapedbracket 3| having a depending arm 5|a terminating in a horizontallyextending portion cooperating with a cam element 52 of the cam 22 (Figs.4 and 6). Secured to the bracket 5| is a resilient arm or clampingelement 33 adapted to engage the pointer 24 of the galvanometer 23 witha complementary clamping element 54 secured to the apparatus frame 34.

The general principles of operation of the above-described apparatus aresubstantially identical with those of the apparatus described in theaforesaid Squibb patent upon which my invention constitutes animprovement. Briefly, assuming the several elements to occupy therelative positions indicated in Figs. 1 and 2 of the drawing and therotation of the shaft 2| to be counterclockwise, as indicated by thearrow in Fig. 2, it will be seen that the cam elements 31 aredisengaging the cam surfaces of the studs '33 secured to the base plateI, so that it is retracted by its biasing spring 35 to the position inwhich the clutch elements 43 of the clutch member 33 engage clutch disk41. At substantially the same time, the cam elements 23 and 23a are justengaging the cam followers 23 and 23a, respectively, and upon rotationof the shaft 2 I, these cam elements are effective to move, against thebias .of the spring l3, the feelers Ila about their pivots l3, |3a, inopposite directions away from the galvanometer needle 24. The earns 43thereafter engage with either of the cam followers 33b of the clutchmember 33 which has been deflected into its path of rotation and, uponrotation by the shaft 2|,eifect movement of the clutch element 33 aboutits pivot 3| to a horizontal position and coincident rotation of theclutch disk 41.

During the aforesaid portion of the cycle of rotation of the shaft 2| inwhich the clutch disk 41 is being moved through an angle proportional tothe defiectionof the clutch member 33 which, in turn, is proportional tothe deflection of the galvanometer needle 24, as described hereinafter,the cam element 52 disengages the arm Bib of the bracket 5|,' releasingthe galvanometer needle 24 from between the clamping elements 53 and34.-

The needle 24, under the influence of its actuating coil 25, nowdeflects to a position corresponding to, and constituting a measure of,any particular electrical condition being measured. As may be seen fromthe configuration of the cam elements 23, 23a and 52, (Figs. 5 and 6),the galvanometer needle 24 is disengaged by the feelers II and Ila andremains unclamped by the elements 53 and 54 during a larger portion ofthe cycle of rotation of the shaft 2|, thereby allowing a maximum timefor the galvanometer needle 24 to come to rest with a deflectioncorresponding to the new value of the condition being measured.

Thereafter, the cam elements 31 engage the cam studs 36 to move the baseplate |3 through a small angle about its pivot |3c, separating theclutch disk 41 and the clutch member 33 so that At about the the member33 is entirely free. same time the cam 52 engages the depending arm 5|aof the bracket 5|, which operates to clamp the galvanometer needle 24between the elements aom'aas 63 and 64 in its new deflected position.Substantially simultaneously with, or shortly after, the clamping of theneedle 24, the cam elements 28 and 23a disengage the cam followers 20and 20a and release the feelers II, Ila, respectively. Prior to therelease it is to be observed the cam elements 23 and 23a maintain thefeelers II and Ila spaced apart by equal amounts from theirneutralposition illustrated in Fig. 1. Upon release, how-- ever, the biasingspring I9 is effective to move the feelers toward each other, closingthe scissors and engaging the galvanometer'needle 24 and the pinassembly 21 in their complementary grips. The spring l8 will return thefeelers II and Ila toward their neutral position at substantially thesame speeds so that if the needle 24 has been deflected through-asubstantial angle, one of the feelers will engage the needle before theother. spring I9 will thereupon move the other feeler about its pivot tothe inclined position corresponding to the deflection of'the needle 24,the lower arm of that feeler, when moving past the neutral position,engaging the pin assembly 21 and deflectingit, together with the clutchmemher 30, about its pivot pin 4|. .Thereupon, the cam elements 23 and23a again separate the feelers II, Ila, the cam 52 disengagesthe arm orelement 5Ia to unclamp thegalvanometer needle from between the elements64 and 54, as described 0 above, and the above described cycle ofoperation is repeated.

From the foregoing, it .is clear that the deflec tion of thegalvanometer needle 24 is measured once each revolution of the shaft 2|,and this defiection is imparted through a torque and/or displacementamplifying mechanism once each cycle to the secondary movable member orclutch member 30. 'If it were desired merely to reproduce intermittentlysuch amplified movements of the 40 pointer 24, the apparatus might stopthere, and

the clutch disk and associated apparatus be omitted. However, it isoften desirable to inof the galvanometer in both magnitude and sense,which movements are added algebraically, or integrated. V

The response of the above apparatus may be adjusted by releasing thestifd 38 in nut 39 and sliding the pin assembly 21 up or down in theslot 28 of the clutch member 30, .thus varying the radius of theoperating arm of the clutch member relative to the radius of the lowerarms of the feelers II and Na about their respective pivots. In additionto thus affording an adjustable connection for operating the clutchmember 30, the 0 collar 4| of the pin assembly 21 serves also to limitthe closing of the scissors-like feelers I I, Ila by the biasing springI9 which, in turn, deter- .mines the clearance between feelers 'II andIla and the pointer 24 when in engaging relationship. This clearance maybe adjusted by adjusting the nut 43, which determines the spacingbetween the conical members 4Iland thus the expansion of the springcollar or sleeve 4|. This may be accomplished from the front of theapparatus since 70 the nut 39-, which restrains the-movement of theright-hand conical member (Fig. 3) is prevented from rotation byengaging the slot 26, as described above.

This adjustment of the clearance between the 75 feelers ll, Ila and thepointer 24 is very desirable example,'when it is desired to securemaximum sensitivity of the apparatus, that is, response of the relayapparatus to minimum deflections of the. pointer 24, a minimum clearanceshould be provided between the feelers I I, -I la and the pointer 24 sothat even infinitesimal deflections of the pointer 24 will be registeredby one or the other of the feelers lI, Ila. On the other hand, if anappreciable clearance be introduced between the feelers l I, Ila, andthe pointer 24, it is clear that deflections of the pointer 24 withinthe range of clearance will be ineffective to produce a move--.

ment of the secondary member 36 or theclutch disk 41. However, incertain instances, this is desirable as, for example, when the quantityto which the galvanometer 26 is responsive has a rapidlyfluctuating-component or ripple which it .is desired to eliminate fromthe reproduced movement of the secondary member 30; or, in

is, to produce a cumulative movement of the disk 41 in a given directionirrespective of variations in the condition to which the galvanometer 26is responsive. It has been found that this error is occasioned by slightdifferences in the timing of the release of the feelers II, llaby thecam elements 23, 23a, respectively. For,

example, if the cam 23 releases its cooperating feeler II by a veryslight interval ahead of the release of the feeler I la, the biasingspring I9 will tend to return the'feeler II into engagement with formaximum flexibility of the apparatus. For

the pointer 24 before engagement thereof by the feeler Ila. The resultis that, for deflections of the pointer 24 within the range of theclearance between the pointer and the feelers II and Ila, the feeler IIwill always deflect the pointer in the same direction by the amount ofthe clearance, and theseunidirectional deflections are cumulative.

ance with my invention, by adjusting the feelers II,- I la along theirpivotal .axes by means of the adjusting screws I5, I5a, respectively,one end of The above error can be eliminated, in accordeach of whichconstitutes the pivotal bearing for its respective feeler pivot pin. Asseen more clearly in Fig. 2, such an adjustment of the feel=-' ers alongtheir pivotal axes moves their associated cam followers 20, 26asubstantially'tangenbe any tendency of the apparatus to creep, as

described above, this may be completely removed by adjusting one or'theother of the screws I5, I5a adjust the corresponding pivoted feeleralong its pivotal axis. When so adjusted, the feelers may be locked inthe adjusted position by means of the locking screw l6.

' "While I have illustrated my improved mechanical relay apparatus asembodied in a control ap- 4 paratus of the type described in theabove-mentioned Squibb patent, for adjusting the setting of apotentiometer disk Ill and a recording pul-, ley 48 in accordance withthe deflections of a 5 galvanometer 28, it will be readily apparenttothose skilled in the art that it is equally applicable to all systemsin which it is desired to reproduce themovement of a primary movablemember with an amplified torque and/or displacement. i

While I have described what I at present consider the preferredembodiment of my invention,

it will be obvious to those skilled in the artthat various changes andmodifications may be made without departing from myfinvention, and I,

. therefore, aim in the appended claims to cover all such changes andmodifications as fall within.

the true spirit and scope of my invention.

What I claim is: l. The combination with a mechanical relayapparatuscomprising a primary movable member; a pair of feelers disposedto engage opposite sides of said member, means for intermittentlyseparating said feelers, means operable during inoperative periods ofsaid separating means to move said feelers substantially into engagementwith said member in any positiong within its range of movement, asecondary member movable in accordance with the position of said feelerswhen engaging said primary member, of means for procuring an adjustableclear ance between said feelers and said member when,

pendent of said primary member for limiting the movement of both of saidfeelers toward each other, of means for adjusting said limiting means tochange said limits of movement of both feel- 50 ers and simultaneouslyto adjust the clearancebetween said feelers and said primary member. 13. The combination with 'a mechanical relay comprising a primary movablemember, a pair of feelers disposed toengage opposite sides of 55 saidmember, means for intermittently separating said feelers, means operableduring inoperative periods of said separating means to move said feelerssubstantially into engagement with said member in any position withinits range of 60 movement, a secondary member movable in,ac-

cordance with the position of said feelers when engaging said primarymember, of an expansible member interposed between said feelers to beengaged thereby when said feelers occupy a 65 given angular position,and means for varying r the expansion of said expansible member tochange said angular position and simultaneously to adjust the clearancebetween sa'id feelers and I said primary member.

70 4. The combination with a mechanical relay comprising a primarymovable member,.a pair of feelers disposed to engage opposite sides ofsaid member, means for intermittently separating said feelers, meansoperable during inopera- 75 tive periods of said separating means tomove mechanical relay I amazes said feelers substantially mm engagementwith said member in any position within its range of- 4 movement, asecondary movable member. of an expansible member ca'rriedby saidsecondary member and interposed between said feelers to be engagedthereby, whereby said secondary member is moved by said feelers inaccordance with'the position of said feelers when engaging said primarymember, and means for varying the expansion of said expansible member toad- Just the clearance between said feelers and member.

5. The combination a mechanical relay' comprising a primary movablemember, a pair of scissors-like feelers disposed to enga e said memberinone of their grips, means for intermittentlyseparating said feelersfrom a given angular position, a biasing spring interconnecting saidfeelers and operable during inoperative periods of said separating meansto move said feelers substantiallyinto engagement with said member inany position within its rangeof movement, a secondary movable member, ofan expansible member carried, by said secondary mem-.

. angular position of said feelers.

s. The combination with a mechanical relay comprising a primary movablemember, a pair of feelers disposed to engage opposite sides of saidmember, means for intermittently separating saidv feelers, meansoperable periods of said separating m to move said feelers substantiallyinto engagement with said member in any position within its range ofmovement, a secondary member movable in accordance with the position ofsaid feelers when engaging said primary member, of means operative-- lyassociated with both of said feelers for procuring an appreciableclearance between said feelers and said member when in engagingrelationship to control the sensitivity of the apparatus, and means forindependently adjusting the timing of the release of said feelers bysaid separating means.

7. The combination with a mechanical relay comprising a primary movablemember, a pair -of feelers disposed to engage opposite. sides of saidmember, means disposed adjacent said feelers operable intermittently toseparate the same, means operable during inoperative periods of saidseparating means to move said feelers substantially into engagement withsaid member in any position within its range of movement, a secondarymember movable in accordance with the position of said feelers whenengaging said primary member, of means operatively associated with bothof said feelers for procuring an appreciable clearance between saidfeelers and said member ng inoperative when in engaging relationship tolimit the sensi-. tivity of the apparatus, and means for indemove saidfeelers substantially into engagement 5 with said member in any positionwithin its range of movement, a secondary member movable in accordancewith the position of said feelers when engaging said primary member, ofmeans for.

procuring an appreciable clearance between said feelers and said memberwhen in engaging relationship to limit to a predetermined degree thesensitivity of the apparatus, and means for independently moving saidfeelers along their respective pivotal axes to adjust the timing of the9. The combination with a mechanical relay apparatus comprisinga'primary movable mem-' ber, a pair of feelers disposed to engageopposite sides of said member, a continuously rotating. 9 cam disposedadjacent said feelers and operable intermittently to separate the same,means operable during inoperative periods of said sep arating means tomove said feelers substantially into engagement with said member in anyposi- 25 tion within its range of movement, a secondary member movablein accordance with the position of said feelers when engaging saidprimary member, of means for procuring an appreciable clearance betweensaid feelers and said member when in engaging relationship to limit thesensitivity of the apparatus, and means for inde} pendently adjustingthe spacing of said feelers with respect to said cam to adjust thetiming of 35 the release of said feelers by said cam.

10. The combination with a mechanical relay apparatus comprising aprimary movable member, a pair of pivotally mounted feelers disposed toengage opposite sides of said member, a continuously rotating camdisposed adjacent said 40 feelers and operable intermittently toseparate the same, means operable during inoperative periods of saidseparating means to move said feelers substantially into engagement withsaid member in any position within its range of movement, a secondarymember movable in accordance with the position of said feelers whenengaging said primary member, of means for'procuring an appreciableclearance between said tionship to limit the sensitivity of theapparatus, and means for independently moving said feelers along theirrespective pivotal axes to adjust thetiming of the release of saidfeelers by said cam. Y

60 which it is pivotally supported, a continuously rotating cam disposedadjacent said feelers and operable intermittently to separate the same,a biasing spring interconnecting said feelers and operable duringinoperative periods of said sep 65 arating means to move said feelerssubstantially into engagement with said member in any position withinits range of movement, a secondary member movable in accordance with theposition of said feelers when engaging said primary mem- 70 ber, ofmeans for procuring an appreciable clearance between said feelers andsaid member when in engaging relationship to limit the sensitivity ofthe apparatus, means for biasing said pivot pins along their axes, andmeans for independ- 75 ently moving said feelers along their respectivefeelers and said member when in engaging relapivotal axes against saidbiasing means to adjust the timing of the release of said feelers bysaid cam.-

'12. The combination with a-mechanical relay apparatus comprising aprimary movable member, a pair of feelers disposed to engage oppositesides of said'member, means for intermittently separating said.feelers,means operable during inoperative periods of said separating meanstogmove said feelers substantially into engagement with said member inany position within its range of movement, a driving clutch membermovable in accordance with the position of said feelers when engagingsaid primary member, adriven clutch member, means for intermitber tointegrate movements ofsaid primary member, of means for procuring anappreciable clearance between said feelers and said member when inengaging relationship to adjust the sensitivity of the apparatus, andmeans for independently adjusting the timing of the release of saidfeelers by said separating means to eliminate creeping of said drivenclutch member due to the clearance between said feelers and said primarymember.

13. Thecombination with a mechanical relay apparatus, having a pair offeelers biased toward each other to move a secondary memberin sense andmagnitude corresponding to deflection of a deflecting member, anappreciable clearance normally being present between said feelers andsaid members to prevent posi e movement of said secondary member uponsmall deflections of said deflecting member, of means for procuringpositive and coextensive movement of said secondary member for smalldeflections of said deflecting member comprising an assembly carried bysaid secondary member for simultaneously varying the positions of saidfeelers until both feelers simultaneously engage said members.

14. A mechanical rel-ay apparatus, having a pair of pivotal feelersbiased into engagement with opposite sides of a deflecting member andseparable. therefrom by cam surfaces the feelers upon release by saidcam surfaces selectively engaging a secondary member to move it inaccordance with the extent and direction of the deflection of saiddeflecting member, characterized by an adjustable member disposedbetween said feelers and carried by said secondary member, means foradjusting said member simultaneously to rotate said feelers about theirpivots substantially to eliminate clearance between said feelers andsaid primary member, and means for timing the release of said feelers bysaid cam surfaces for simultaneous movement toward said primary andsecondary members comprising means for bodily moving each of saidfeelers along the axis of its pivot thereby to vary its relation withrespect to its associated cam surface.

15. The combination with a mechanical relay having a pair of feelerspivoted intermediate their ends and biased toward a closed position toengage on one side of their pivots a deflecting member and uponsubstantial deflection thereof to engage a secondary member on theopposite sides of. their pivots to move it an amount corof said feelersto positions simultaneously to en gage said deflecting member and saidassembly.

A 1 18. The combination with a mechanical relay comprising a primarymovable member having a given range of movement, a pair of pivotallymounted feelers disposed to engage opposite sides of said member; meansdisposed adjacent said 20 feelers and operable intermittently toseparate the same, means operable during inoperative periods of saidseparating means to move said feelers substantially into engagement withsaid member in any position within its range of move- 25 ment, and asecondary member movable in accordance with the position of said feelerswhen I ensui g said primary member, of means for independently movingsaid feelers along their respective pivotal axes to adjust the timing ofthe 0 release of said feelers.

17. The combination with a mechanical relay apparatus comprising aprimary movable memvber. a pair of scissors-like feelers disposed to env2,o7s,s sa responding to said deflection an appreciable cleargage saidmember in one of their Kril each of said feelers including aunitarypivot pin by which it is pivotally supported, a continuously rotatingcam disposed adjacent said feelers and operable intermittently toseparate the same.- a

biasing spring connecting said feelers and operable during inoperativeperiods of said separating means to move said feelers substantially intoengagement with said member, and a secondary member movable inaccordance with the position of said feelers when engaging said primarymember, of means for biasing each of said pivot pins along its axis, andmeans for independently moving each of said feelers along its pivotalaxis against said biasing means to adjust the timing of the release ofsaid feelers by said cam.

18. A mechanical relay apparatus. having a pair of pivotalfeelers biasedinto engagement with opposite sides of a deflecting member and separabletherefrom by cam surfaces. the" feel-- ers upon release by said camsurfaces selectively engaging a secondary member to move it inaccordance with the extent and direction of the deflection ofsaid,deflecting member, characterized by means for timing the release ofsaid feelers by said cam surfaces for simultaneous movement toward saidprimary and secondary members comprising means for bodily moving each ofsaid feelers along the axis of its pivot thereby to vary the relation ofeach feeler with respect to its as mciated cam surface.

JOHN F. 'scnocx

